The dopamine-containing neurons of the substantia nigra project to the dorsolateral prefrontal cortex and the striatum. In the rhesus monkey, electrolytic lesions of the prefrontal cortex or the related parts of the striatum, or depletion of dopamine in the prefrontal cortex, impair performance of delayed alternation, a test of cognitive function. However, bilateral destruction of the substantia nigra in a pilot animal had little, if any, effect. This project was undertaken to establish the generality of that negative finding.